Variable geometry exhaust ducts for aircraft gas turbine engine installations frequently employ an axisymmetric arrangement of overlapping flap and seal members to define the periphery of the exhaust duct. By providing an intermediate, transverse hinge in the flap and seal members, prior art ducts have achieved convergent-divergent arrangements wherein the duct may be configured to define a variable area throat which is necessary for optimized engine performance, particularly in high speed aircraft installations using afterburning for thrust augmentation.
Such prior art axisymmetric nozzles direct the exhaust gas aftward from the aircraft generally along a central axis. Certain alternative designs exist for attempting to provide a practical arrangement for selectively diverting the exhaust gas from this axial centerline in order to achieve vectored thrust for enhancing aircraft maneuverability. Such thrust vectoring nozzle configurations have typically not been adaptable to the axisymmetric nozzles described hereinabove and further are usually limited to redirecting exhaust gas in only a single plane. An additional drawback of prior art vectoring nozzle has been the increased weight of the actuators and exhaust gas directing surfaces at the aftmost portion of the exhaust duct and aircraft, thus adding additional weight at the most undesirable location in the aircraft due to stability and balance considerations.
What is needed is a thrust vectoring exhaust duct design which is adaptable to both convergent-divergent exhaust arrangements as well as lightweight, axisymmetric configurations.